AM Hounds Dogs

The AM Beagles ( AM Canum Venaticorum , AM CVn ) is a cataclysmic variable double star in the constellation of the Beagles . She became the progenitor of a whole class of variable stars . Based on parallax measurements using the Hubble Space Telescope , it can be calculated that the system is about 2000 light years away (610 parsecs ) from Earth, that it has its own motion 34.25 ± 0.88 mas • year ⁻¹ at position angle 67 , 0 ± 1.7 ^[2] .

AM Hounds Dogs
Double star
The position of the star in the constellation
Observational data ( Epoch J2000.0 )
Type of	Cataclysmic variable
Right ascension
Declination
Distance	1976 ++ 440 −-300
Visible magnitude ( V )	V max = +14.02 m , V min = +13.7 m , P = +0.28 d [2]
Constellation	Hounds Dogs
Astrometry
Proper motion (μ)	RA: 36.6 [3] mas per year Dec: 25.5 [3] mas per year
Parallax (π)	1.65 ± 0.30 [2] mas
Specifications
Spectral class	DBp [4]
Color Indicator ( B - V )	−0.23 [5]
Color Index ( U - B )	−1.01 [5]
Variability	AM CVn [6]
Orbit elements
Period ( P )	1,028.7322 ± 0.0003 s. (17: 08.732 ± 0.018 min) [6] years
Inclination ( i )	43 ± 2 ° [6] ° v
Other designations AM CVn, EGGR 91, HZ 29, GSC 03018-02523, PG 1232 + 379, WD 1232 + 37, AAVSO 1229 + 38.
Information in databases
SIMBAD	data
The star has 2 components Their parameters are presented below:

In the years 1939-1940, there were studies of weak white dwarfs using the 18-inch (46 cm) Schmidt telescope at the Palomar Observatory . Part of the research was done around the north pole of the galaxy to exclude stars of spectral classes O, B, and A, since these massive short-lived stars are usually concentrated along the plane of the Milky Way , where star formation takes place.

In 1947, a list of faint blue stars was compiled for observable objects by Milton L. Humason and Fritz Zwicky ^[7] . Their blue tint indicates a relatively high effective temperature . The 29 star on their list (HZ 29) had the most specific spectrum from the set. It shows the absence of hydrogen lines in the spectrum , but broad, diffuse lines of neutral ( non-ionized ) helium ^[8] . So poor white dwarfs were found by hydrogen . In 1962 , this star was observed by a photoelectric detector and it was found that the luminosity varies in magnitude with a period of 18 minutes. The light curve showed variations that are displayed by a double sinusoid ^[9] . Later, flickering was observed, which forced us to offer mass transfer in the system ^[2] .

AM Hounds-Brush Curve with a 330-Min Period

The model developed to explain the observations was that AM Beagles was a binary system consisting of a pair of white dwarfs in a very tight orbit. The main one is a more massive white dwarf consisting of carbon / oxygen , while the secondary is a less massive white dwarf of helium , without hydrogen , but with traces of heavy elements ^[2] . (In some variables of the AM Hounds Dog type , a secondary can be a semi-degenerate object , such as a subdwarf of spectral class B instead of a helium white dwarf ). The system emits gravitational waves during rotation, which reduce the stress-energy stress tensor , causing a decrease in the orbit ^{[10] [11]} . This transmission occurs because the secondary star fills the Roche lobe , created by the gravitational interaction between two stars ^[2] .

The mass transfer rate between white dwarfs is estimated at about 7⋅10 ^-9 solar masses per year, which leads to the creation of an accretion disk around the white dwarf ^[6] . The energy output from the mass flow to this accretion disk makes the main contribution to the visual luminosity of the entire system; the disc eclipses both white dwarfs . The temperature of this disk is about 30 000 K ^[6] .

High-speed photometry of the system shows several periods of change in the luminosity of a variable. The main period 1,028.73 seconds (17min. 8.73s) is the orbital period of the pair ^[12] . The secondary period of 1,051 seconds (17min 31s) is believed to be caused by superhumps on the light curve, which has a period slightly longer than the orbital period. Superhorbs can be the result of relative lengthening of an accretion disk in combination with precession. An elliptical disk precesses around a white dwarf for a period of time slightly longer than the orbital period, resulting in a small change in the orientation of the disk along each element of the orbit ^[13] .

Usually this star system exhibits only luminosity variations of 0.05 ^m . However, the AM Hounds Dogs star systems are also new-like objects that can randomly generate intense flashes. AM Hounds Dogs demonstrated this behavior twice from 1985 to 1987 . In 1986, the flash caused an increase in luminosity of Δm = 1.07 ± 0.03 ^m and lasted 212 seconds. The amount of energy released during this event is estimated at 2.7⋅10 ³⁶ Erg . ^[14] . These flashes are caused by short-term thermonuclear helium synthesis, which accumulates along the outer shell of the primary star ^[15] .